You know, I think it would be cool if Anne were revealed to have been one of the runaway kids Jennifer hung with when she first hit Salem until Jennifer went back to the "perfect Hortons" and forgot all about Anne & everyone else. Anne ended up going into foster care (a good home, really) and becoming a successful career woman, but that feeling of abandonment and "not being good enough" stuck with her which causes her resentment of Jennifer and the rest of the Hortons. IMO, it's something so simple, yet logical & plays into actual show history.

Maybe Jen tampered with Anne's shampoo.

The Anne/Marlena scene was a small moment. Anne tried to use her to take down Daniel. Marlena is the the head of the hospital ethics committee, or something.